1. Field of the Invention
This invention relates to audio signal processing and, in particular, to methods and systems for adapting a gain of an audio output signal.
2. Related Art
Audio systems may process audio from many different sources of audio signals that may contain music and/or speech. Audio signals containing music may be stored on a CD, a DVD or on any other suitable storage medium. Recent developments in compression schemes such as MPEG allow for audio signals with music and/or speech from different genres and artists to be stored on a storage medium and combined in a playlist to be played out to a user. The audio signals are typically derived from different audio sources having different signal and dynamics compression levels. The audio sources may be from different tracks that have different signal level ranges. When played out, for example in a playlist, the different tracks may be perceived by the user as being at different loudness levels.
In a vehicle environment, audio perceived by passengers may contain the audio signal itself and noise, which may include road tire noise, aerodynamics noise and engine noise. Audio signals played in a vehicle environment should be perceivable to the user, which means that the audio signal loudness should exceed the noise present in the vehicle. The overall audio level, which includes the audio signal and the noise, should not exceed a level that may result in hearing damage or be painful to the listener.
Audio signals from different sources may be difficult to hear if the signals are played at different loudness levels. The problem is aggravated in environments having loud ambient noise. There is a need for systems that control audio signal output levels to permit a listener to perceive the audio signals from different tracks at a consistent sound level. There is a need for systems that provide consistent sound levels in environments having loud ambient noise.